In recent years, as part of measures to address environmental problems, an attention has been given to a hybrid vehicle, an electric vehicle, a fuel-cell vehicle, and the like that can run by driving force obtained from a rotating electrical machine (electric motor). Such a vehicle also vibrates during running under the influence of driving force of the vehicle itself, a state of a road surface, and others. Therefore, techniques of suppressing vibrations of the vehicle have been proposed.
Japanese Patent Laying-Open No. 2005-020831 discloses a driving force controller for reducing back and forth vibrations of an electric-powered vehicle, wheels of which are driven by a motor. This driving force controller includes: a standard driving force calculation unit for calculating standard driving force corresponding to an operation state of the vehicle; a road surface uneven portion detection unit for detecting a road surface uneven portion over which wheels pass during running; an additional driving force calculation unit for calculating additional driving force for the wheels, which additional driving force reduces wheel speed variations caused by the passage over the uneven portion; a composite driving force calculation unit for calculating composite driving force by adding up the additional driving force and the standard driving force; and a motor driving force control unit for controlling driving force of the motor such that the composite driving force is provided to the wheels.
According to the driving force controller described in this publication, when the wheels pass over a road surface uneven portion, the wheels are provided with the composite driving force, which is a sum of the additional driving force which reduces wheel speed variations caused by the passage over the uneven portion, and the standard driving force corresponding to the vehicle operation state. It is thereby possible to reduce back and forth vibrations of the vehicle body, caused by the variations in wheel speed during the passage over the uneven portion.
Some hybrid vehicles have an engine and two rotating electrical machines, and use the engine and one of the rotating electrical machines as a driving source, and use the other of the rotating electrical machines as an electric power generator. In such hybrid vehicles as well, it is desired to reduce the vibrations thereof. However, the driving force controller described in Japanese Patent Laying-Open No. 2005-020831 has no description about such hybrid vehicles.